another valves question

fourmations

hi all

a couple of tube questions I havent been able to google successfully..

i have done lots of reading and have come to believe
that position 1 (nearest input) is the main pre-amp
and has the biggest influence on the sound.

so.. can i buy one each of a few types and just
try them in position 1 and see where i get
(my amp gets muddy and loses clarity and treble when driven)

also, i believe that i can use alternatives to the 12ax7's it takes
can i mix the types, (4 12ax7's and one alternative)

any good links welcome

thanks

4

rgds

Karl Hungus

I don't know about mixing preamp tube types, but trying out different brands in V1 is definetly doable.

fourmations

thanks karl

i have a 25yr old tube amp and dont know what to do with it!
its lovely when clean and crunchy or driven harder with pedals
but its own amp gain gets messy when upped,
Im trying to skim down on effects nowadays and let the amps
tones come through

I cant afford to buy a load of sets of tubes (5 x 12ax7's)
just to hear what they sound like,

im no map expert at all and realistically i dont
know if the tubes even need changing or if the amp needs
a full service or what,

I'm irrationally paranoid about bringing it to an amp tech...
(i'm afraid they will do a half-arsed job, charge me for a million things,
also the fact that i dont know how this amp sounds at it's very best
means I'm a sitting duck for a big bill with any sort of improvement made)

Maybe i just have trust issues!!

rgds

4

punchdrunk

preamp tubes don't need to be biased so you can experiment away!

12at7's will sound a bit cleaner,and 12ax7's have the most gain 12au7's are mostly used as phase inverters and reverb valves as far as i remember

punchdrunk

what amp is it?

fourmations

http://www.boards.ie/vbulletin/showthread.php?t=2055097801&highlight=studiomaster

thats all the info i have!

the manual only says what valves it takes (2 6L6GC and 5 12ax7's)
no recommended brands etc

its an unknown amp so getting info has been impossible

i read a review of harmony central likening it to a Mesa Mk IV
(but as we all know the reviews on harmony are subjective)

I emailed Eurotubes and they dont know the amp either

Regards

4

Voodu Child

fourmations wrote: »

I'm irrationally paranoid about bringing it to an amp tech...
(i'm afraid they will do a half-arsed job, charge me for a million things,
also the fact that i dont know how this amp sounds at it's very best
means I'm a sitting duck for a big bill with any sort of improvement made)

Unfortunately, it will need a visit to an amp tech at some stage; you don't buy a 25 year old amp without accepting it's going to need some kind of work every now and then.

The capacitors in a typical valve amp have a literal 'shelf life' - the chemicals in them degrade and at some point just go bad. Could be 10 or 15 years before the need replacing, but one thing is for sure - they WILL need replacing at some stage. A good amp tech will just gut ALL the caps and replace them if he knows it hasnt been done in the last ten years or so.

Other things like pots go rusty and need cleaning/replacing too, solder joints degrade over time, and valves will usually go 'bad' long before they give up altogether. Bias can wander as well, and mis-biased power valves never sound their best. So you could have an amp that sounds terrible, but is working, so you assume everything is fine.

The point of all this is that a professional service on an old amp is a MUST every now and then. If you don't have a service history (yes, seriously) for your amp, you have to assume that it could do with one sooner rather than later.

I don't know if this is any help to you - a full service and re-valve won't be cheap, could be looking at a couple of hundred if he does a full and proper job. That's the price you pay for tone unfortunately, particularly with vintage valve amps.

fourmations

thanks voodoo

couple of hundred I can live with...

Im just afraid that it will run out of hand
and i will be like the dumb blond getting charged 1000's for a car service!

Would it be reasonable to ask for an estimate
or is that something that cant be worked out until
he's well into the job?

rgds

4

It wasn't me!

Yeah, for whatever it's worth, I've a 24 year old Marshall JCM800 and it's just been too costly and too much hassle to keep, so I'm going to be selling it and getting a modern amp. It just cost too much to keep sounding like that, and as a student, I can't afford that.

Eoin Madsen

fourmations wrote: »

the manual only says what valves it takes (2 6L6GC and 5 12ax7's)
no recommended brands etc

Brand recommendations are always subjective anyway. There's no one "best" valve for an amp. You are correct in thinking that you can mix and match 12AX7 other 12A*7 preamp valves. Experiment away.

The sequence in which you place different preamp valves will affect the gain structure. Low gain valves after high gain valves or vice versa etc.

voodoo_child has said pretty much everything that needs to be said, I think. Valve amps are work, old or new. The older ones just sooner. If it came with valves in, I'd change them all. Chances are they're past their prime. Get a matched pair of 6L6s, and have someone bias the amp when they're put in. They'll last a good year or two of modest playing. I'm not sure who does biasing around. Maybe one of the guys in Musician Inc?

Asking a tech for a ballpark quote is perfectly reasonable. They may withhold a quote for a full service until they've evaluated the amp. Frankly, they should do that part for free, but this is Ireland so I assume you might have to front some cash. Extra costs should not appear once they've begun work unless they did a bad job of assessing it to begin with.

How servicable it is depends on a few things. If it's hard to find a schematic for it, you may have a little difficulty given the shortage of highly experienced techs around. If the circuit board is wired point to point rather than printed it generally makes for a easier amp to work on too.

You amp looks delicious by the way.

Eoin Madsen

It wasn't me! wrote: »

Yeah, for whatever it's worth, I've a 24 year old Marshall JCM800 and it's just been too costly and too much hassle to keep, so I'm going to be selling it and getting a modern amp. It just cost too much to keep sounding like that, and as a student, I can't afford that.

Say it ain't so. What's wrong with it at the moment?

It wasn't me!

Haven't played it in ages what with the LC and one thing and another and whatnot, but last I checked, the gain had pretty much crapped out and I was left with an under-volumed mangy clean sound.

punchdrunk

happened to my 2203 a while back,sounds like you've a dodgy EL34...

Eoin Madsen

punchdrunk wrote: »

happened to my 2203 a while back,sounds like you've a dodgy EL34...

Could really be anything really. Any dodgy valve, a dying cathode resistor, a shorted OT even.

It'll be tricky to shift if it's got a fault though.

It wasn't me!

Ah, I'll be getting it fully sorted and such before selling, so it shouldn't be too bad, just can't afford to keep an amp that's that much hassle.

Eoin Madsen

Get the transformers checked out anyway, above all else. Any other fault is dirt cheap to fix tbh.

And let me know when you're selling it.

It wasn't me!

Heh, will do on both counts.